Fiber Laser Cutting of Mild Steel

Fiber laser for materials processing have undergone a rapid development in the pastseveral years. As fiber laser provides a combination of high beam quality and awavelength that is easily absorbed by metal surfaces, the named future laser isexpected to challenge the CO2 and Nd:YAG lasers in the area of metal cutting. This thesis studied the performance of fiber laser cutting mild steel. In the literature review part, it introduced the laser cutting principle and the principle of fiber laser including the newest development of fiber laser cuttingtechnology. Because the fiber laser cutting mild steel is a very young technology, a preliminary test was made in order to investigate effect of the cutting parameters on cut quality. Then the formal fiber laser cutting experiment was madeby using 3 mm thickness S355 steel with oxygen as assistant gas. The experimentwas focused on the cut quality with maximum cutting speed and minimum oxygen gas pressure. And the cut quality is mainly decided by the kerf width, perpendicularity tolerance, surface roughness and striation patterns. After analysis the cutting result, several conclusions were made. Although the best result got in the experiment is not perfect as predicted, the whole result of the test can be accepted. Compared with CO2 laser, a higher cutting speed was achieved by fiber laser with very low oxygen gas pressure. A further improvement about the cutting quality might be possible by proper selection of process parameters. And in order to investigate the cutting performance more clearly, a future study about cutting different thickness mild steel and different shape was recommended.

Tuning the design procedures for laser processed microwave mechanics

This research has been focused at the development of a tuned systematic design methodology, which gives the best performance in a computer aided environment and utilises a cross-technological approach, specially tested with and for laser processed microwave mechanics. A tuned design process scheme is also presented. Because of the currently large production volumes of microwave and radio frequency mechanics even slight improvements of design methodologies or manufacturing technologies would give reasonable possibilities for cost reduction. The typical number of required iteration cycles could be reduced to one fifth of normal. The research area dealing with the methodologies is divided firstly into a function-oriented, a performance-oriented or a manufacturability-oriented product design. Alternatively various approaches can be developed for a customer-oriented, a quality-oriented, a cost-oriented or an organisation-oriented design. However, the real need for improvements is between these two extremes. This means that the effective methodology for the designers should not be too limited (like in the performance-oriented design) or too general (like in the organisation-oriented design), but it should, include the context of the design environment. This is the area where the current research is focused. To test the developed tuned design methodology for laser processing (TDMLP) and the tuned optimising algorithm for laser processing (TOLP), seven different industrial product applications for microwave mechanics have been designed, CAD-modelled and manufactured by using laser in small production series. To verify that the performance of these products meets the required level and to ensure the objectiveness ofthe results extensive laboratory tests were used for all designed prototypes. As an example a Ku-band horn antenna can be laser processed from steel in 2 minutes at the same time obtaining a comparable electrical performance of classical aluminium units or the residual resistance of a laser joint in steel could be limited to 72 milliohmia.

Selective catalytic reduction of nitrogen oxides with ammonia in forced unsteady state reactors - Case based reasoning and mathematical model simulation reasoning

The application of forced unsteady-state reactors in case of selective catalytic reduction of nitrogen oxides (NOx) with ammonia (NH3) is sustained by the fact that favorable temperature and composition distributions which cannot be achieved in any steady-state regime can be obtained by means of unsteady-state operations. In a normal way of operation the low exothermicity of the selective catalytic reduction (SCR) reaction (usually carried out in the range of 280-350°C) is not enough to maintain by itself the chemical reaction. A normal mode of operation usually requires supply of supplementary heat increasing in this way the overall process operation cost. Through forced unsteady-state operation, the main advantage that can be obtained when exothermic reactions take place is the possibility of trapping, beside the ammonia, the moving heat wave inside the catalytic bed. The unsteady state-operation enables the exploitation of the thermal storage capacity of the catalyticbed. The catalytic bed acts as a regenerative heat exchanger allowing auto-thermal behaviour when the adiabatic temperature rise is low. Finding the optimum reactor configuration, employing the most suitable operation model and identifying the reactor behavior are highly important steps in order to configure a proper device for industrial applications. The Reverse Flow Reactor (RFR) - a forced unsteady state reactor - corresponds to the above mentioned characteristics and may be employed as an efficient device for the treatment of dilute pollutant mixtures. As a main disadvantage, beside its advantages, the RFR presents the 'wash out' phenomena. This phenomenon represents emissions of unconverted reactants at every switch of the flow direction. As a consequence our attention was focused on finding an alternative reactor configuration for RFR which is not affected by the incontrollable emissions of unconverted reactants. In this respect the Reactor Network (RN) was investigated. Its configuration consists of several reactors connected in a closed sequence, simulating a moving bed by changing the reactants feeding position. In the RN the flow direction is maintained in the same way ensuring uniformcatalyst exploitation and in the same time the 'wash out' phenomena is annulated. The simulated moving bed (SMB) can operate in transient mode giving practically constant exit concentration and high conversion levels. The main advantage of the reactor network operation is emphasizedby the possibility to obtain auto-thermal behavior with nearly uniformcatalyst utilization. However, the reactor network presents only a small range of switching times which allow to reach and to maintain an ignited state. Even so a proper study of the complex behavior of the RN may give the necessary information to overcome all the difficulties that can appear in the RN operation. The unsteady-state reactors complexity arises from the fact that these reactor types are characterized by short contact times and complex interaction between heat and mass transportphenomena. Such complex interactions can give rise to a remarkable complex dynamic behavior characterized by a set of spatial-temporal patterns, chaotic changes in concentration and traveling waves of heat or chemical reactivity. The main efforts of the current research studies concern the improvement of contact modalities between reactants, the possibility of thermal wave storage inside the reactor and the improvement of the kinetic activity of the catalyst used. Paying attention to the above mentioned aspects is important when higher activity even at low feeding temperatures and low emissions of unconverted reactants are the main operation concerns. Also, the prediction of the reactor pseudo or steady-state performance (regarding the conversion, selectivity and thermal behavior) and the dynamicreactor response during exploitation are important aspects in finding the optimal control strategy for the forced unsteady state catalytic tubular reactors. The design of an adapted reactor requires knowledge about the influence of its operating conditions on the overall process performance and a precise evaluation of the operating parameters rage for which a sustained dynamic behavior is obtained. An apriori estimation of the system parameters result in diminution of the computational efforts. Usually the convergence of unsteady state reactor systems requires integration over hundreds of cycles depending on the initial guess of the parameter values. The investigation of various operation models and thermal transfer strategies give reliable means to obtain recuperative and regenerative devices which are capable to maintain an auto-thermal behavior in case of low exothermic reactions. In the present research work a gradual analysis of the SCR of NOx with ammonia process in forced unsteady-state reactors was realized. The investigation covers the presentationof the general problematic related to the effect of noxious emissions in the environment, the analysis of the suitable catalysts types for the process, the mathematical analysis approach for modeling and finding the system solutions and the experimental investigation of the device found to be more suitable for the present process. In order to gain information about the forced unsteady state reactor design, operation, important system parameters and their values, mathematical description, mathematicalmethod for solving systems of partial differential equations and other specific aspects, in a fast and easy way, and a case based reasoning (CBR) approach has been used. This approach, using the experience of past similarproblems and their adapted solutions, may provide a method for gaining informations and solutions for new problems related to the forced unsteady state reactors technology. As a consequence a CBR system was implemented and a corresponding tool was developed. Further on, grooving up the hypothesis of isothermal operation, the investigation by means of numerical simulation of the feasibility of the SCR of NOx with ammonia in the RFRand in the RN with variable feeding position was realized. The hypothesis of non-isothermal operation was taken into account because in our opinion ifa commercial catalyst is considered, is not possible to modify the chemical activity and its adsorptive capacity to improve the operation butis possible to change the operation regime. In order to identify the most suitable device for the unsteady state reduction of NOx with ammonia, considering the perspective of recuperative and regenerative devices, a comparative analysis of the above mentioned two devices performance was realized. The assumption of isothermal conditions in the beginningof the forced unsteadystate investigation allowed the simplification of the analysis enabling to focus on the impact of the conditions and mode of operation on the dynamic features caused by the trapping of one reactant in the reactor, without considering the impact of thermal effect on overall reactor performance. The non-isothermal system approach has been investigated in order to point out the important influence of the thermal effect on overall reactor performance, studying the possibility of RFR and RN utilization as recuperative and regenerative devices and the possibility of achieving a sustained auto-thermal behavior in case of lowexothermic reaction of SCR of NOx with ammonia and low temperature gasfeeding. Beside the influence of the thermal effect, the influence of the principal operating parameters, as switching time, inlet flow rate and initial catalyst temperature have been stressed. This analysis is important not only because it allows a comparison between the two devices and optimisation of the operation, but also the switching time is the main operating parameter. An appropriate choice of this parameter enables the fulfilment of the process constraints. The level of the conversions achieved, the more uniform temperature profiles, the uniformity ofcatalyst exploitation and the much simpler mode of operation imposed the RN as a much more suitable device for SCR of NOx with ammonia, in usual operation and also in the perspective of control strategy implementation. Theoretical simplified models have also been proposed in order to describe the forced unsteady state reactors performance and to estimate their internal temperature and concentration profiles. The general idea was to extend the study of catalytic reactor dynamics taking into account the perspectives that haven't been analyzed yet. The experimental investigation ofRN revealed a good agreement between the data obtained by model simulation and the ones obtained experimentally.

Particle Size Analysis of Pharmaceutical Powders by Laser Diffraction

Raaka-aineen hiukkaskoko on lääkekehityksessä keskeinen materiaaliparametri. Lääkeaineen partikkelikoko vaikuttaa moneen lääketuotteen tärkeään ominaisuuteen, esimerkiksi lääkkeen biologiseen hyväksikäytettävyyteen. Tässä diplomityössä keskityttiin jauhemaisten lääkeaineiden hiukkaskoon määrittämiseen laserdiffraktiomenetelmällä. Menetelmä perustuu siihen, että partikkeleista sironneen valon intensiteetin sirontakulmajakauma on riippuvainen partikkelien kokojakaumasta. Työn kirjallisuusosassa esiteltiin laserdiffraktiomenetelmän teoriaa. PIDS (Polarization Intensity Differential Scattering) tekniikka, jota voidaan käyttää laserdiffraktion yhteydessä, on myös kuvattu kirjallisuusosassa. Muihin menetelmiin perustuvista analyysimenetelmistä tutustuttiin mikroskopiaan sekä aerodynaamisen lentoajan määrittämiseen perustuvaan menetelmään. Kirjallisuusosassa esiteltiin myös partikkelikoon yleisimpiä esitystapoja. Työn kokeellisen osan tarkoituksena oli kehittää ja validoida laserdiffraktioon perustuva partikkelikoon määritysmenetelmä tietylle lääkeaineelle. Menetelmäkehitys tehtiin käyttäen Beckman Coulter LS 13 320 laserdiffraktoria. Laite mahdollistaa PIDS-tekniikan käytön laserdiffraktiotekniikan ohella. Menetelmäkehitys aloitettiin arvioimalla, että kyseinen lääkeaine soveltuu parhaiten määritettäväksi nesteeseen dispergoituna. Liukoisuuden perusteella väliaineeksi valittiin tällä lääkeaineella kyllästetty vesiliuos. Dispergointiaineen sekä ultraäänihauteen käyttö havaittiin tarpeelliseksi dispergoidessa kyseistä lääkeainetta kylläiseen vesiliuokseen. Lopuksi sekoitusnopeus näytteensyöttöyksikössä säädettiin sopivaksi. Validointivaiheessa kehitetyn menetelmän todettiin soveltuvan hyvin kyseiselle lääkeaineelle ja tulosten todettiin olevan oikeellisia sekä toistettavia. Menetelmä ei myöskään ollut herkkä pienille häiriöille.

Suojakaasuseoksen koostumuksen vaikutus CO2-laser-MAG-hybridihitsauksessa

Hitsaavassa teollisuudessa kilpailukyvyn säilyttäminen edellyttää hitsauksen tehokkuuden nostoa. Niinpä metalliteollisuus etsii kuumeisesti uusia yhä tehokkaampia hitsausmenetelmiä. CO2-laserin ja MAG:in yhdistelmän muodostamalla hybridihitsauksella saadaan aikaan syvä tunkeuma kuten laserhitsauksessa, mutta sallitaan laserhitsausta väljemmät railotoleranssit. Samalla muodonmuutokset vähenevät huomattavasti verrattuna perinteiseen kaarihitsaukseen. Kaariavusteisessa laserhitsauksessa yhdistetään laserhitsaukseen perinteinen kaarihitsaus eli MIG/MAG-, TIG- tai plasmahitsaus. Menetelmää voidaan kutsua myös hybridihitsaukseksi ja sillä hyödynnetään molempien prosessien edut välttyen yksittäisten prosessien haitoilta. Prosessin haittapuolena on parametrien suuri määrä, joka on rajoittanut menetelmän käyttöönottoa. Diplomityössä tutkittiin suojakaasuseoksen koostumuksen vaikutusta rakenneteräksen CO2-laser-MAG-hybridihitsauksessa. Laserhitsauksen ja MAG-hitsauksen suojakaasuvirtaukset yhdistettiin siten, että heliumseosteinen suojakaasu tuotiin MAG-polttimen kaasukuvun kautta. Suojakaasun heliumpitoisuus nostettiin niin korkeaksi, että estettiin laserhitsauksen muodostaman plasman syntyminen. Samalla hitsauskokeissa opittiin paremmin ymmärtämään prosessia ja sen parametrien riippuvuutta toisiinsa. Tutkitut suojakaasuseokset koostuivat heliumista, argonista ja hiilidioksidista. Hitsauskokeiden perusteella havaittiin, että suojakaasuseoksen optimaalinen heliumpitoisuus on 40-50 %. Tällöin laserin tunkeumaa häiritsevää plasmapilveä ei synny ja prosessi on stabiili. Päittäisliitosten hitsauksessa suojakaasuseoksen 2 %:n CO2-pitoisuudella saadaan aikaan hyvin vähän huokosia sisältävä hitsi, jonka tunkeumaprofiilin muoto ja liittymä perusaineeseen on juoheva. Pienaliitoksilla 7 %:n CO2-pitoisuudella prosessi pysyy stabiilina ja vähäroiskeisena. Tunkeuma hieman levenee hitsin keskeltä ja hitsin liittyminen perusaineeseen on juoheva.CO2-laser-MAG-hybridihitsauksella aikaansaadaan laadukkaita hitsejä taloudellisesti, mikäli käytetyt parametrit ovat oikein valittuja. Parametrit on sovitettava jokaiseen hitsaustapaukseen erikseen, eikä niitä välttämättä voida suoraan käyttää toisessa tapauksessa.

Optimizing nozzle flow in laser cutting

The purpose of this study was to investigate different laser cutting nozzles, nozzle flows and possibilities to improve nozzle flow. Another goal was to design new nozzle configuration in which laser cutting would succeed with better cutting speed and smaller gas consumption. Nozzles and nozzle flows were studied with various methods. Computational fluid dynamics was used to calculate old, convergent nozzles and new convergent-divergent nozzles. Measurement apparatus was used to measure both nozzle types. In cutting tests different materials were cut with new nozzles. With the use of design convergent-divergent nozzles 25 % better cutting speed and 33 % smaller gas consumption were achieved when cutting quality was good. Computational fluid dynamics was also discovered to be useful aid in nozzle design.

The effects of selective estrogen receptor modulators on the death of breast cancer cells and osteoblastic cells

Selektiivisten estrogeenireseptorin muuntelijoiden (serm) vaikutus rintasyöpäsolujen ja luun solujen kuolemaan Selektiiviset estrogeenireseptorin muuntelijat (SERMit) ovat ryhmä kemialliselta rakenteeltaan erilaisia yhdisteitä jotka sitoutuvat solunsisäisiin estrogeenireseptoreihin toimien joko estrogeenin kaltaisina yhdisteinä tai estrogeenin vastavaikuttajina. Tamoksifeeni on SERM –yhdiste, jota on jo pitkään käytetty estrogeenireseptoreita (ER) ilmentävän rintasyövän lääkehoidossa. Tamoksifeeni sekä estää rintasyöpäsolujen jakaantumista että toisaalta aikaansaa niiden apoptoosin eli ohjelmoidun solukuoleman muuntelemalla ER-välitteisesti kohdesolun geenien ilmentymistä. Viimeaikaiset tutkimustulokset ovat kuitenkin osoittaneet tamoksifeenilla olevan myös nopeampia, nongenomisia vaikutusmekanismeja. Tässä väitöskirjatyössä tutkimme niitä nopeita vaikutusmekanismeja joiden avulla tamoksifeeni vaikuttaa rintasyöpäsolujen elinkykyyn. Osoitamme että tamoksifeeni farmakologisina pitoisuuksina aikaansaa nopean mitokondriaalisen solukuolemaan johtavan signallointireitin aktivoitumisen rintasyöpäsoluissa. Tämän lisäksi tutkimme myös tamoksifeenin aiheuttamaan mitokondriovaurioon johtavia tekijöitä. Tutkimustuloksemme osoittavat että ER-positiivisissa rintasyöpäsoluissa tamoksifeeni indusoi pitkäkestoisen ERK-kinaasiaktivaation, joka voidaan estää 17-beta-estradiolilla. Tamoksifeenin aikaansaama nopea solukuolema on pääosin ER:sta riippumaton tapahtuma, mutta siihen voidaan vaikuttaa myös ER-välitteisin mekanismein. Sen sijaan epidermaalisen kasvutekijäreseptorin (EGFR) voitiin osoittaa osallistuvan tamoksifeenin nopeiden vaikutusten välittämiseen. Tämän lisäksi vertailimme myös estradiolin ja eri SERM-yhdisteiden kykyä suojata apoptoosilta käyttämällä osteoblastiperäisiä soluja. Pytyäksemme vertailemaan ER-isotyyppien roolia eri yhdisteiden suojavaikutuksissa, transfektoimme U2OS osteosarkoomasolulinjan ilmentämään pysyvästi joko ERalfaa tai ERbetaa. Tulostemme mukaan sekä estradioli että uusi SERM-yhdiste ospemifeeni suojaavat osteoblastin kaltaisia soluja etoposidi-indusoidulta apoptoosilta. Sekä ERalfa että ERbeta pystyivät välittämään suojavaikutusta, joskin vaikutukset erosivat toisistaan. Lisäksi havaitsimme edellä mainitun suojavaikutuksen olevan yhteydessä muutoksiin solujen sytokiiniekspressiossa. Tietoa SERM-yhdisteiden anti-ja proapoptoottisten vaikutusmekanismeista eri kohdekudoksissa voidaan mahdollisesti hyödyntää kehiteltäessä uusia kudosspesifisiä SERM-yhdisteitä.

Laser Doppler -vibrometrin käyttöönotto tärinämittauksissa

Tässä insinöörityössä otettiin käyttöön VTI Technologies Oy:lle hankittu laser Doppler - vibrometri, joka mittaa tärinää perustuen valon Dopplerin siirtymään. Työn tavoitteena oli perehtyä mittauslaitteistoon, muodostaa sille näytteenottolaitteisto ja käytännössä arvioida sen kyvykkyyttä mitata tärinää ja tuottaa uutta informaatiota. Työn teoreettisessa osuudessa perehdytään laser Doppler -vibrometrin teknologiaan ja toimintaperiaatteeseen sekä värähtelevien systeemien dynamiikkaan ja mallintamiseen. Työn käytännön osuuden suorittamiseksi perehdyttiin myös tärinätestauslaitteiston toimintaan, analogiasignaalin näytteenottoon sekä diskreettiin Fourier-muunnokseen perustuvaan signaalin spektrianalyysiin. Työssä käsitellään myös laser-mittauksen kohinalähteitä ja spektrianalyysin virhelähteitä. Työn käytännön osuudessa ohjelmoitiin Labview-mittausohjelmisto näytteenottolaitteistolle. Mittausohjelmistolla voidaan näytteistää vibrometrin mittaussignaalia ja muodostaa sen taajuusspektri. Mittauskohteita tässä työssä olivat kulmakiihtyvyystäryttimen mekaanisen liikkeen mittaus ja elementtikiekkosahan terän värähtelyjen mittaus. Mittaustulokset kulmakiihtyvyystäryttimestä osoittivat sen mekaanisen liikkeen säröytyvän voimakkaasti, johtuen todennäköisesti sen testialustan rakenteesta. Testialustan rakennetta tullaan kehittämään ja mittaukset toistetaan. Mittaustuloksiin elementtikiekkosahasta tuli suhtautua epäillen, koska mittaussignaalin intensiteetti oli erittäin heikko. Mittausten onnistuminen Laser Doppler -vibrometrillä edellyttää riittävää mittauskohteesta takaisinheijastuneen laser-valon intensiteettiä. Mittaustulokset osoittivat laser Doppler -vibrometrin olevan hyödyllinen työkalu tutkivassa tärinämittauksessa. Mittauskohteet, joiden pinta heijastaa huonosti valoa ja joihin ei voi asentaa erityistä heijastavaa teippiä, ovat kuitenkin haaste ja asettavat rajoituksen laser Doppler -vibrometrin käyttömahdollisuuksille. Tämän työn mittaustuloksia voidaan käyttää kulmakiihtyvyystäryttimen uusintamittausten vertailukohtana, kun arvioidaan kehitystyön onnistumista. Tätä työtä voidaan käyttää myös laser Doppler -vibrometrin ohjekirjana tärinämittauksissa.

The effects of some variables on CO2 laser-MAG hybrid welding

The CO2-laser-MAG hybrid welding process has been shown to be a productive choice for the welding industry, being used in e.g. the shipbuilding, pipe and beam manufacturing, and automotive industries. It provides an opportunity to increase the productivity of welding of joints containing air gaps compared with autogenous laser beam welding, with associated reductions in distortion and marked increases in welding speeds and penetration in comparison with both arc and autogenous laser welding. The literature study indicated that the phenomena of laser hybrid welding are mostly being studied using bead-on-plate welding or zero air gap configurations. This study shows it very clearly that the CO2 laser-MAG hybrid welding process is completely different, when there is a groove with an air gap. As in case of industrial use it is excepted that welding is performed for non-zero grooves, this study is of great importance for industrial applications. The results of this study indicate that by using a 6 kW CO2 laser-MAG hybrid welding process, the welding speed may also be increased if an air gap is present in the joint. Experimental trials indicated that the welding speed may be increased by 30-82% when compared with bead-on-plate welding, or welding of a joint with no air gap i.e. a joint prepared as optimum for autogenous laser welding. This study demonstrates very clearly, that the separation of the different processes, as well as the relative configurations of the processes (arc leading or trailing) affect welding performance significantly. These matters influence the droplet size and therefore the metal transfer mode, which in turn determined the resulting weld quality and the ability to bridge air gaps. Welding in bead-onplate mode, or of an I butt joint containing no air gap joint is facilitated by using a leading torch. This is due to the preheating effect of the arc, which increases the absorptivity of the work piece to the laser beam, enabling greater penetration and the use of higher welding speeds. With an air gap present, air gap bridging is more effectively achieved by using a trailing torch because of the lower arc power needed, the wider arc, and the movement of droplets predominantly towards the joint edges. The experiments showed, that the mode of metal transfer has a marked effect on gap bridgeability. Transfer of a single droplet per arc pulse may not be desirable if an air gap is present, because most of the droplets are directed towards the middle of the joint where no base material is present. In such cases, undercut is observed. Pulsed globular and rotational metal transfer modes enable molten metal to also be transferred to the joint edges, and are therefore superior metal transfer modes when bridging air gaps. It was also found very obvious, that process separation is an important factor in gap bridgeability. If process separation is too large, the resulting weld often exhibits sagging, or no weld may be formed at all as a result of the reduced interaction between the component processes. In contrast, if the processes are too close to one another, the processing region contains excess molten metal that may create difficulties for the keyhole to remain open. When the distance is optimised - i.e. a separation of 0-4 mm in this study, depending on the welding speed and beam-arc configuration - the processes act together, creating beneficial synergistic effects. The optimum process separation when using a trailing torch was found to be shorter (0-2 mm) than when a leading torch is used (2-4 mm); a result of the facilitation of weld pool motion when the latter configuration is adopted. This study demonstrates, that the MAG process used has a strong effect on the CO2-laser-MAG hybrid welding process. The laser beam welding component is relatively stable and easy to manage, with only two principal processing parameters (power and welding speed) needing to be adjusted. In contrast, the MAG process has a large number of processing parameters to optimise, all of which play an important role in the interaction between the laser beam and the arc. The parameters used for traditional MAG welding are often not optimal in achieving the most appropriate mode of metal transfer, and weld quality in laser hybrid welding, and must be optimised if the full range of benefits provided by hybrid welding are to be realised.

Superconducting properties and their enhancement in ReBa2Cu3O7-delta (RE = Y and Gd) films prepared by pulsed laser deposition

Due to font problem on the tilte field the titlte of the thesis is corrected here. The title of the thesis is: Superconducting properties and their enhancement in ReBa₂Cu₃O₇-delta (RE = Y and Gd) films prepared by pulsed laser deposition

Product costing model for laser welded hollow core steel panels

The aim of the study was to create an easily upgradable product costing model for laser welded hollow core steel panels to help in pricing decisions. The theory section includes a literature review to identify traditional and modern cost accounting methodologies, which are used by manufacturing companies. The theory section also presents the basics of steel panel structures and their manufacturing methods and manufacturing costs based on previous research. Activity-Based costing turned out to be the most appropriate methodology for the costing model because of wide product variations. Activity analysis and the determination of cost drivers based on observations and interviews were the key steps in the creation of the model. The created model was used to test how panel parameters affect the costs caused by the main manufacturing stages and materials. By comparing cost structures, it was possible to find the panel types that are the most economic and uneconomic to manufacture. A sensitivity analysis proved that the model gives sufficiently reliable cost information to support pricing decisions. More reliable cost information could be achieved by determining the cost drivers more accurately. Alternative methods for manufacturing the cores were compared with the model. The comparison proved that roll forming can be more advantageous and flexible than press brake bending. However, more extensive research showed that roll forming is possible only when the cores are designed to be manufactured by roll forming. Due to that fact, when new panels are designed consideration should be given to the possibility of using roll forming.

Spectroscopic monitoring during laser welding of aluminium alloy

The mechanical properties of aluminium alloys are strongly influenced by the alloying elements and their concentration. In the case of aluminium alloy EN AW-6060 the main alloying elements are magnesium and silicon. The first goal of this thesis was to determine stability, repeatability and sensitivity as figures of merit of the in-situ melt identification technique. In this study the emissions from the laser welding process were monitored with a spectrometer. With the information produced by the spectrometer, quantitative analysis was conducted to determine the figures of merit. The quantitative analysis concentrated on magnesium and aluminium emissions and their relation. The results showed that the stability of absolute intensities was low, but the normalized magnesium emissions were quite stable. The repeatability of monitoring magnesium emissions was high (about 90 %). Sensitivity of the in-situ melt identification technique was also high. As small as 0.5 % change in magnesium content was detected by the spectrometer. The second goal of this study was to determine the loss of mass during deep penetration laser welding. The amount of magnesium in the material was measured before and after laser welding to determine the loss of magnesium. This study was conducted for aluminium alloy with nominal magnesium content of 0-10 % and for standard material EN AW-6060 that was welded with filler wire AlMg5. It was found that while the magnesium concentration in the material changed, the loss of magnesium remained fairly even. Also by feeding filler wire, the behaviour was similar. Thirdly, the reason why silicon had not been detected in the emission spectrum needed to be explained. Literature research showed that the amount of energy required for silicon to excite is considerably higher compared to magnesium. The energy input in the used welding process is insufficient to excite the silicon atoms.

Spectrometrical Monitoring of Laser Sintering Process of Ceramic Material

This thesis is done as a part of project called FuncMama that is a project between Technical Research Centre of Finland (VTT), Oulu University (OY), Lappeenranta University of Technology (LUT) and Finnish industrial partners. Main goal of the project is to manufacture electric and mechanical components from mixed materials using laser sintering. Aim of this study was to create laser sintered pieces from ceramic material and monitor the sintering event by using spectrometer. Spectrometer is a device which is capable to record intensity of different wavelengths in relation with time. In this study the monitoring of laser sintering was captured with the equipment which consists of Ocean Optics spectrometer, optical fiber and optical lens (detector head). Light from the sintering process hit first to the lens system which guides the light in to the optical fibre. Optical fibre transmits the light from the sintering process to the spectrometer where wavelengths intensity level information is detected. The optical lens of the spectrometer was rigidly set and did not move along with the laser beam. Data which was collected with spectrometer from the laser sintering process was converted with Excel spreadsheet program for result’s evaluation. Laser equipment used was IPG Photonics pulse fibre laser. Laser parameters were kept mainly constant during experimental part and only sintering speed was changed. That way it was possible to find differences in the monitoring results without fear of too many parameters mixing together and affecting to the conclusions. Parts which were sintered had one layer and size of 5 x 5 mm. Material was CT2000 – tape manufactured by Heraeus which was later on post processed to powder. Monitoring of different sintering speeds was tested by using CT2000 reference powder. Moreover tests how different materials effect to the process monitoring were done by adding foreign powder Du Pont 951 which had suffered in re-grinding and which was more reactive than CT2000. By adding foreign material it simulates situation where two materials are accidently mixed together and it was studied if that can be seen with the spectrometer. It was concluded in this study that with the spectrometer it is possible to detect changes between different laser sintering speeds. When the sintering speed is lowered the intensity level of light is higher from the process. This is a result of higher temperature at the sintering spot and that can be noticed with the spectrometer. That indicates it could be possible to use spectrometer as a tool for process observation and support the idea of having system that can help setting up the process parameter window. Also important conclusion was how well the adding of foreign material could be seen with the spectrometer. When second material was added a significant intensity level raise could be noticed in that part where foreign material was mixed. That indicates it is possible to see if there are any variations in the material or if there are more materials mixed together. Spectrometric monitoring of laser sintering could be useful tool for process window observation and temperature controlling of the sintering process. For example if the process window for specific material is experimentally determined to get wanted properties and satisfying sintering speed. It is possible if the data is constantly recorded that the results can show faults in the part texture between layers. Changes between the monitoring data and the experimentally determined values can then indicate changes in the material being generated by material faults or by wrong process parameters. The results of this study show that spectrometer could be one possible tool for monitoring. But to get in that point where this all can be made possible much more researching is needed.